DESCRIPTION:(provided by applicant) Maintaining balance during dynamic activities such as walking provides a stable platform for functioning of visual and vestibular systems. Successful motor patterns for head and gaze stabilization have been described for laboratory tasks of seated rotations. However, a task like walking poses a different solution to the problems of maintaining head and gaze stabilization. The broad aim of this project is to examine the integration between sensory and motor systems that contributes to dynamic balance during functional activities. Specifically, this study will delineate motor strategies used to maintain dynamic balance and gaze stability during walking in healthy individuals. These data will serve as baseline measures for studying patients with vestibular dysfunction and older adults with a fall history. Twenty healthy young adults will participate in this study. Subjects will perform four walking tasks. In the first task, subjects will walk at their natural pace over a 15 m walkway. In the second task, subjects will walk while orienting their gaze on a distant stationary target. This task should enhance head and gaze stabilization. In a third task, subjects will walk in total darkness to eliminate visual input. The fourth task involves viewing a head mounted target while walking. This task will suppress the vestibulo-occular reflex and provide information regarding the relative role of gaze stabilization to dynamic balance. Head and trunk movements will be measured using angular rate sensors. Eye-in-head movements will be measured using an infrared limbus tracking system. Head-on-trunk with respect to trunk motion, and eye-in head with respect to head motion will be examined across the frequency spectrum of walking for each condition. These data will provide information on the role of vision and gaze stabilization in maintaining dynamic balance while walking. Motor patterns identified in healthy individuals will 1) provide options for successful substitution strategies in treatment of patients with vestibular dysfunction and 2) provide strategies for dynamic balance used in fall prevention programs for older adults.